Refrigeration system including metering and distributing means



D- 5. WILSON Feb. 11, 1964 REFRIGERATION SYSTEM INCLUDING METERING ANDDISTRIBUTING MEANS Filed Jan. 18, 1962 FIG. l

, INVENTOR.

DAV") S WILSON FIG. 3

ATTORNEY.

United States Patent 3,12%,743 REFRIGERATHQN SYSTEM INCLUDING METER- INGAND DKSTRHEUTING MEANS David S. Wilson, East Syracuse, N.Y., assignor toCarrier (Iorporation, Syracuse, FLY, a corporation of Dela- Ware FiledJan. 18, 1962, Ser. No. 167,007 3 Claims. (61. 62-5tl4) This inventionrelates to refrigeration systems and more particularly to arefrigeration system having novel refrigerant metering and distributingmeans therein comprising a capillary tube and a distributor.

In refrigeration systems comprising a compressor, a condenser, expansionmeans, and a multiple circuit evaporator, difiiculty has beenencountered in assuring adequate and uniform distribution of refrigerantfrom the expansion means to the evaporator over a wide range of openating conditions. The expansion means may comprise either a thermalexpansion valve or a capillary tube. Normally the refrigeration systemutilizing a thermal expasion valve includes a distributor mechanismdisposed between the thermal expansion valve and each circuit of theevaporator. Within the conventional distributor mechanism there is anorifice, which produces a secondary pressure drop, for assuring properdistribution of refrigerant to each evaporator circuit. Cost-wise thethermal expansion valve is expensive by comparison to a capillary tube.Accordingly, it is often desirable to utilize a capillary tube in placeof a thermal expansion valve in a refrigeration system.

To utilize capillary expansion means in a refrigeration system operableover a Wide range of operating conditions, particular care must be givento the rate of refrigerant flow and to the saturated condensingtemperature. Water cooled condensers present little problem, forcondensing conditions are closely controlled. Air-eooled condensers,however, operate in extremes of outdoor temperature. The refrigerationsystem utilizing an air-cooled condenser should be designed for storingrefrigerant to backload the condenser coil so as to assure adequaterefrigerant feed through the capillary tube at all operating conditions.

One method of feeding refrigerant to a multiple circuit evaporator is toprovide a separate capillary tube for each circuit. There is difficulty,however, in balancing the feed of refrigerant to each circuit of theevaporator. Too, it is expensive to utilize a plurality of capillarytubes in place of a single capillary tube and a distributor mechanism.

It has been proposed that a single capillary tube be used to feedrefrigerant to a conventional thermal expansion valve distributormechanism having an orifice therein. However, the usual distributormechanism appears to be unsuitable for refrigeration systems havingcapillary expansion means because the high velocity and turbulencewithin the distributor mechanism required for good distribution producesa secondary pressure drop. In refrigeration systems utilizing a thermalexpansion valve, distributor pressure drop is not necessarily aliability, however, in refrigeration systems having capillary tubeexpansion means, pressure drop in the distributor mechanism isundesirable. Capillary control performance is adversely affected.Distributor mechanisms having low pressure drop usually do not feedrefrigerant uniformly to each of a plurality of circuits.

An object of this invention is to provide a refrigeration system havingcapillary tube expansion means feeding a plurality of evaporatorcircuits wherein the disadvantages and deficiencies of priorconstructions are obviated.

An object of the present invention is to provide a re- BiZdJ iB PatentedFeb. 11, 1964 frigeration system having refrigerant metering anddistributing means comprising a capillary tube and a refrigerantdistributor wherein the disadvantages and deficiencies of prior systemsare obviated.

Another object of this invention is to provide a refrigeration systemwith improved metering and distributing means comprising a capillarytube and a distributor for uniformly feeding refrigerant from thecapillary tube to each of the circuits of a multiple-circuit evaporator.Other objects of my invention will be readily perceived from thefollowing description.

This invention relates to a refrigeration system comprising thecombination of a compressor, a condenser, a multiple-circuit evaporator,and means connecting the condenser and the evaporator comprising acapillary tube and distributor means, the distributor means comprising ahousing having an inlet bore and a plurality of outlet bores therein,each outlet bore being in communication at one end with the inlet boreand at the other end with a line adapted to communicate with a circuitof the evaporator, a generally conical member in the distributor housingfor directing refrigerant uniformly into each outlet bore, the capillarytube being connected at one end to the condenser and at the other endwithin the inlet bore of the distributor housing, the end of thecapillary tube within the distributor housing being positioned adjacentthe apex of the generally conical member so as to maximize pressure dropwithin the capillary tube and mini mize pressure drop within thedistributor means.

The invention will now be described by reference to the attached drawingwherein like numerals in each of the several views refer to likeelements and wherein:

FIGURE 1 is a diagrammatic view of a refrigeration system embodying therefrigerant metering and distributing means of the present invention;

FIGURE 2 is an exploded perspective view, with parts broken away, of therefrigerant metering and distributing means of the present invention;and

FiGURE 3 is a cross-sectional view of the refrigerant metering anddistributing means of the present invention.

Referring to FIGURE 1 of the drawing, there is shown the usualrefrigeration system including compressor 14) connected to condenser 11by discharge line 12. Refrigerant flows from condenser 11 to eachcircuit of evaporator 14 through refrigerant metering and distributingmeans 13.

Though the evaporator is shown as having only four circuits it will beobvious that more circuits may be used, it being understood that eachcircuit will be connected to the refrigerant metering and distributingmeans 13 through a separate line or tube 17. Each of the circuits 21,2.2., 23 and 24 of the evaporator are connected to header 25. From theheader, refrigerant passes through suction line 26, accumulator 27 insuction line 26 proximate the outlet from header and is returned tocompressor 1d.

FIGURE 2 shows an exploded perspective view of the refrigerant meteringand distributing means of the present invention. Such means comprisesbody 29 having therein an inlet bore 30 communicating with capillarytube 15 and outlet bores 31, each communicating with a line 17.Centrally of the outlet bores within the distributor body 29 there is aconical-shaped member 33. The end of the capillary tube may bepositioned within and secured to capilary positioner 34. The capillarypositioner is inserted into inlet bore 3t} until the face thereof abutsa shoulder in body 29. Retainer ring is provided behind capillarypositioner 34 to secure the positioner in place within inlet bore 35).The apex of the cone or conical-shaped member 33 is adjacent the end ofthe capillary tube 15 and does not extend into or restrict the end ofthe capillary tube. The opening from the capillary tube is unrestrictedand cone 33 serves only to direct liquid refrigerant uniformly from thecapillary tube into each of the outlet bores 31.

For convenience in manufacture, the ends of each of the outlet bores 31may be counterbored as at 37 to receive each of the lines 17. The linesare each suitably connected to the distributor by means of solder, forexample.

Connector support 40 is secured at one end to distributor body 29 and atthe other end to capillary tube -15. The support maintains apredetermined length of tube axial with respect to inlet bore 30.

It has been experimentally determined that the straight length ofcapillary tube adjacent the end thereof connected within the distributorbody 29 is critical in assuring proper distribution of refrigerant toeach of the circuits of the evaporator. In the presently preferredembodiment of the invention the end of capillary tube must be straightfor a distance of at least twenty times the internal diameter of thecapillary tube to assure proper feeding of refrigerant from thecapillary tube. Where the capillary tube was bent at a lesser distancefrom its end, it was found that the loading upon the evaporator wasunequal. However, when the capillary tube was of the proper straightlength, then for the identical system, as aforetested, the evaporatorwas loaded according to the design requirements. Accordingly, it must beconcluded that this straight length of the end of the capillary tube isan important part of the present invention.

Refrigerant compressor 19 forwards high pressure vaporous refrigerantthrough discharge line 12 to condenser 11. The refrigerant withincondenser .11 passes in heat exchange relationship with a coolingmedium, either air or water, to condense and subcool the refrigerant.Such condensed and subcooled refrigerant passes through refrigerantmetering and distributor means 13 to evaporator 14-. As the refrigerantpasses through each of the circuits of the evaporator it expands andcools the air passing over the heat exchange surface of the evaporator.The expanded refrigerant is collected in header and returned tocompressor 10 through accumulator 27 and suction line 26.

The purpose of the capillary tube is to reduce the pressure of theliquid refrigerant leaving the high pressure condenser to a suitablepressure required in the evaporator to provide the required coolingperformance of the evaporator and to maintain a refrigerant flow raterequired by the refrigeration system as a whole under the specificoperating conditions encountered at any given time. The pressurereduction obtained with a capillary tube of specified internal bore andtube length is a function of the frictional resistance of the liquidrefrigerant passing through the tube and the point in the tube wherepressure is reduced to the saturation point and vaporization into agaseous state starts to occur. From this point to the end of thecapillary the resistance is increased due to the presence of gas bubblesin the liquid stream which increases the volume of the refrigerantmixture, thereby increasing the velocity and resulting in an increasedpressure drop through the remainder of the capillary tube. Thus it isseen that the flow through a capillary tube is dependent upon thepressure of the liquid entering the tube, which creates the drivingforce, and upon the temperature of the liquid entering the tube, whichdetermines the point at which the refrigerant vaporizes and bubblesstart to occur in the tube.

in a refrigeration system employing an air-cooled condensing coil, boththe condensing pressure and the liquid temperature can be varied by theamount of charge introduced into the refrigeration system. The greaterthe charge in the system, the more liquid refrigerant that will beback-loaded into the condenser coil, thereby reducing the condensingsurface. There is a resultant increase in head pressure and an increasein subcooling surface, ac-

companied by a lower liquid temperature. In a refrigeration systememploying an accumulator in the suction line a given amount ofrefrigerant can be stored in the accumulator. When needed, thisrefrigerant can be introduced into the refrigeration system to load thecondenser coil in or er to maintain the required flow rate under a widerange of air temperature over the condenser coil, articularly duringwinter or low temperature load conditions. Thus it is seen that thecapillary tube as employed in this type of system can maintain asatisfactory performance over a large range of condensing conditions.These performance characteristics can be obtained only if the expansionof liquid refrigerant is accomplished largely within the capillary tubeitself. In refrigeration systems which have a secondary expansionthrough a distributor orifice, the refrigerant flow control obtained byreducing a liquid temperature is greatly limited.

By virtue of the present invention the pressure drop occurring as theliquid flows through the refrigerant metering and distributing means isprimarily confined to that occurring within the capillary tube. Thepressure drop within distributor body 29 is minimized so as to assuremore uniform distribution of refrigerant from capillary tube 15 to eachcircuit 21, 22, 23 and 24 of evaporator 14. The proper feeding ofrefrigerant to each of the circuits of the evaporator is important, forpoor refrigerant distribution results in unequal evaporator loading andin reduction in evaporator capacity.

By the present invention there has been provided a novel refrigerantmetering and distributing means for direct expansion evaporators havinga plurality of circuits. The refrigerant metering and distributing meansassures optimum performance under varying conditions of load. Thepresent invention maintains homogeneous mixture of liquid refrigerantand vaporous refrigerant in the refrigerant metering and distributingmeans until equal portions of liquid and vapor are delivered to eachevaporator circuit. The novel refrigerant metering and distributingmeans is relatively inexpensive to manufacture and satisfactorilyovercomes the problem of unequal distribution encountered with previousrefrigerant metering and distributing means in refrigeration systemsutilizing capillary tube expansion means.

While I have described a preferred embodiment of my invention, it Willbe understood that my invention is not limited thereto, since it may beotherwise embodied within the scope of the following claims.

I claim:

1. In a refrigeration system, the combination of a compressor, acondenser, a multi-circuit evaporator and means connecting saidcondenser to said evaporator comprising a capillary tube and distributormeans, said distributor means comprising a housing having an inlet boreand a plurality of outlet bores, each outlet bore being in communicationat one end with said inlet bore and at the other end with a line adaptedto communicate with a circuit of the evaporator, a generally conicalmember in said distributor housing for directing refrigerant from thecapillary tube into the outlets, means for positioning an end of saidcapillary tube within the inlet bore of said distributor housing, meansfor retaining said positioning means in place within said housing, theopposite end of said tube communicating with the condenser, the end ofthe capillary tube within said distributor housing being positionedadjacent the apex of the generally conical member, and a support memberfor supporting said tubing, the pressure drop within the capillary tubebeing larger than the pressure drop within the distributor means.

2. A refrigeration system as in claim 1 wherein the end of the capillarytube adjacent the generally conical member is straight for a distance ofat least twenty inside diameters of die capillary tube to assure properfeeding of refrigerant to the distributor means from the capillary tube.

3. Refrigerant metering and distributing means for use in arefrigeration system comprising a capillary tube and a distributorconnected thereto, said distributor including a housing having an inletand a plurality of outlets, each of said outlets adapted to be connectedto a multiplecircuit evaporator in the refrigeration system, a generallyconically-shaped member in said distributor for directing refrigerantfrom the end of said capillary tube into each outlet, means forpositioning an end of said capillary tube Within said housing adjacentthe comically-shaped 10 member, means for retaining said positioner inplace in 0 said housing, said capillary tube and distributor being soconstructed that the pressure drop within the capillary tube is largerthan the pressure drop Within the distributor, and a support member forsupporting said tubing.

References Cited in the file of this patent UNITED STATES PATENTS2,082,403 Larkin June 1, 1932 2,461,876 Boyle Feb. 15, 1949 2,489,680Shoemaker Nov. 29, 1949

3. REFRIGERANT METERING AND DISTRIBUTING MEANS FOR USE IN AREFRIGERATION SYSTEM COMPRISING A CAPILLARY TUBE AND A DISTRIBUTORCONNECTED THERETO, SAID DISTRIBUTOR INCLUDING A HOUSING HAVING AN INLETAND A PLURALITY OF OUTLETS, EACH OF SAID OUTLETS ADAPTED TO BE CONNECTEDTO A MULTIPLECIRCUIT EVAPORATOR IN THE REFRIGERATION SYSTEM, A GENERALLYCONICALLY-SHAPED MEMBER IN SAID DISTRIBUTOR FOR DIRECTING REFRIGERANTFROM THE END OF SAID CAPILLARY TUBE INTO EACH OUTLET, MEANS FORPOSITIONING AN END OF SAID CAPILLARY TUBE WITHIN SAID HOUSING ADJACENTTHE CONICALLY-SHAPED MEMBER, MEANS FOR RETAINING SAID POSITIONER INPLACE IN SAID HOUSING, SAID CAPILLARY TUBE AND DISTRIBUTOR BEING SOCONSTRUCTED THAT THE PRESSURE DROP WITHIN THE CAPILLARY TUBE IS LARGERTHAN THE PRESSURE DROP WITHIN THE DISTRIBUTOR, AND A SUPPORT MEMBER FORSUPPORTING SAID TUBING.